1. Field of the Invention
The invention relates to the field of electron beam lenses and deflectors and more particularly to their array structures.
2. Brief Description of the Prior Art
The array structure of an electron beam lens and deflector gun is comprised of two parallel plate subassemblies: a plurality of lens plates and two fine deflector plates. The lens plates are essentially a grid of apertures, while the two deflector plates are sets of parallel conductive blades. The blades of one plate are oriented orthogonally to the other plate. The lens plates are commonly composed of silicon while the fine deflector plates are composed of a conductive metal.
Array structures have to be precisely aligned. To accomplish this, previous array structures have included optical alignment techniques with glass rodding and mechanical referencing to supporting rings as a means to axially align, space and fasten together the array assembly. This requires considerable precision opto-mechanical fixturing to achieve assembly and an elaborate supporting superstructure or cage to hold the subassemblies in position. See, e.g., U.S. Pat. No. 4,200,794 to Newberry et al., assigned to the Control Data Corporation.
For electron beam array lithography, the array design has an outside nominal dimension of approximately one inch. In this environment, opto-mechanical fixturing becomes prohibitively difficult due to the lack of area on the perimeter of the array elements. It is similarly prohibitively difficult to incorporate a supporting superstructure in the limited space available surrounding a one inch array.